Selective fire converter and rate reducer



Jan. 9, 1962 A. M. FRANCHl 3,

SELECTIVE FIRE CONVERTER AND RATE REDUCER Filed July 27, 1960 2 Sheets-Sheet 1 1962 A. M. FRANCHI SELECTIVE FIRE CONVERTER AND RATE REDUCER Filed July 27, 1960 2 Sheets-Sheet 2 3,015,993 Patented Jan. 9, 1962 fiice 3,015,993 SELECTIVE FEE CONVERTER AND RATE REDUCER Attrlio Mario Franchi, Brescia, Italy, assignor to Soc. p. Az. Luigi Franchi, Brescia, Italy Filed July 27, 1960, Ser. No. 45,711 Claims priority, application 'Italy Aug. 5, 1959 4 Claims. (Cl. 89-431) This invention relates to automatic firearms suitable for operation in semi-automatic or full automatic fire.

An object of this invention is to provide a trigger mechanism for such firearms capable of ensuring continuous or full automatic fire at a substantially reduced rate, the rate of fire being the number of shots per minute the arm is capable of firing when set to full automatic action. The reduced rate of fire is advantageous and desirable as it saves the ammunition and allows the shooter to correct the aim soon after the first shots have been fired.

Another object is to provide an improved trigger mechanism where the operating cycle of the hammer and of the delaying elements are as smooth as possible and shock is reduced between cooperating elements such as teeth, arrests, catches, etc. Still-another object of this invention is to provide a new cooperation between thehammer and the trigger so as to render the mechanism more sensitive when firing single shots in semi-automatic fire.

In a general way the invention comprises: a delay mass coaxial with the hammer and engaged with the latter during the recoil stroke, the hammer forming part of a toggle link having a quick release at its dead centre; the hammer together with the delay mass being placed on the recoil path of the breech bolt, causes cocking of the mechanism by the recoil of the breech bolt; spring loaded elements locking temporarily the delay mass in its retracted position against action of a spring; unlocking of the delaying mass occurs a little before the breech bolt reaches closed position, and is controlled by a step situated on the breech bolt; also an oscillating sear fixed on the trigger pivot and spring controlled so as to move in the path of a tooth situated on the hammer for locking the hammer in cocked position, the arrangement being such that the spring tends to move the sear out of the path of an action tooth provided on the trigger, this against the thrust of the hammer which tends to move the sear into the said path. I

It will be seen from what follows that the sear, and its spring constitute a damper for the hammer; thus reducing the shock between the cooperating components. It will be also seen that the toggle link which comprises the hammer, disengages the latter from any contact with the breech bolt on its last portion of the recoil path, thus reducing wear of contacting surfaces, moreover the toggle link provides the trigger mechanism with another means of delaying movements of the hammer thus contributing to the reduction of the firing rate.

Further characteristics and advantages will be seen from the following description and reference to the accompanying drawings, in which the FIGURES 1 to 4 are side views of the trigger mechanism in four difierent phases of action. More precisely:

FIGURE 1 shows the mechanism at the limit of 'the recoil phase of the hammer;

FIGURE 2 shows the mechanism cocked, set for single shot action;

FIGURE 3 shows the mechanism after a single shot has been fired, and

FIGURE 4 shows the mechanism set for continuous fire action.

The trigger mechanism is contained in a rectangular, fiat casing 10 of steel sheet, the drawings show the casing with one side plate removed to show the mechanism. The

ing with pivot 12.

counterclockwise.

other side plate llsupports three fixed pivots 12, 14 and 16 that extend toward the other side plate.

On pivot 12, freely mounted side by side, are hammer 17 and delay mass 18, both having a form of a two arm lever. The arm 17a of the hammer and the arm 18a of the delay mass normally interfere with the recoil path of the breech bolt 20, the said breech bolt contains a firing pin, its rear part 21 protruding from the rear of the breech bolt. The arm 17a' of hammer 17 moves in this same plane as the firing pin and by striking the extremity 21 ofthe latter cause action. The arm 18a of the delaymass has a semicylindrical seat 22 housing the head 23a of a push rod 23. The tail part of the push rod slides in an opening 24 of the back plate 10a of casing 10. A helical compression spring 25 is compressedon shank of rod 23 between the plate 10a and a collar on rod 23 so as to push the head 23a into seat 22. The reciprocal arrangement of seat 22, pivot 12 and ope-ning 24 ensures that the delay-mass 18 is continuously under action of spring 25 The reciprocal arrangement of pivot 12, pin 26 and of the opening in the back plate 10a is in this case such as to from a toggle link whereas the hammer swings pin 26 crosses the imaginary straight line joining the said open- Thus, conditions being as shown in FIG. 1, spring 28 tends toswing the hammer 17 clockwise, while under conditions shown in FIGS. 2 to 4, hammer 17 under action of spring 28 tends to swing The other lever arm of hammer 17 carries a lateral finger 17b protruding into the path of the delay mass 18. The delay mass 18 engages the lateral finger 17b by either an abutment surface 30 situated at the rootof arm 18a or by another abutment surface 31 on the face of a tooth 18b which forms the other lever arm of the mass 18. Considering the conditions shown on FIG. 1, the angular distance between finger 17 b and abutment surface 30 relatively to pivot 12, is such, that towards the end of forward (counterclockwise) movement of delay mass 18 towards situation shown on FIG. 2, the surface 30 meets 'finger 17b and takes it across the dead centre, thus permitting the spring 28 to swing the hammer towards the extremity 21 of firing pin. The abutment surface 31 of a tooth 18b immediately, adjacent to finger 17b as shown in FIG. 1, constitutes a stop for hammer 17 impeding any counterclockwise movement. Hence, as a system, the parts 17b, 30 and 31 form a lost motion connection between hammer and delay mass, the said connection becoming active in the end part of swing of the delay mass towards breech bolt 20, as described above.

With tooth 18b cooperates a pawl 32 fixed to a lever :arm 33 pivoted on pivot 14, and controlled by a spring '34, which tends to bring pawl 32 on the path of tooth 18b. As shown in FIG, 1, where delay mass 18 and hammer 17 are both at their extreme clockwise swing,

'the pawl engages the tooth 18b, thus locking the mass 18 ing surfaces of lever 35 and arm 33 are such, thatthe above mentioned swing of lever 35 produces a counterclockwise swing of arm 33 together with pawl 32, disengaging the latter from tooth 18b, and thus unlocking the delay mass 18.

The trigger 40 and sear 41 are pivoted on pivot 16. Wound around this pin is a spring 42, with one end bearing against pivot 12, the other end bearing against trigger 40, tending to keep the trigger in a neutral position, as shown on FIGS. 1 and 2, where the trigger bears against a limit stop 43, fixed to casing 10. The rear part of the trigger 40 forms an arm 44, cooperating with a selector 45. The selector is formed by a pin able to rotate in supports in side plates of casing 10, and. has a diametral incut 46. The selector is controlled by a wing (not shown) on the outside of casing and can be placed in three positions corresponding to: safety, semi-automatic or single shot firing and full automatic or continuous firing. These positions are depicted in FIGS. -1, 2 and 4, respectively.

The sear 41, T formed, is suspended on pin 16 passing through an eyelet 47 parallel to the top bar of T; this suspension permits oscillating and sliding motions of the sear. The forearm 41a of scar 41 cooperates with a tooth 170 provided on hammer 17 for locking it in the cocked position, i.e immediately after the hammer passed the dead centre checked by the surface 30 and finger 17b, as shown in FIG, 2. i

The body of trigger 40 houses a plunger 50 (FIG. 2) pushed against the vertical bar of the T sear under action of a compression spring, thus the Seat 41 tends to slide forwards on the pin 16 and rotate sufficiently to bring its front arm 41a into the path of the hammer tooth 170. The plunger spring is weaker than the hammer spring 28, thus as shown on FIG. '2, the sear 41 is pushed backwards by the hammer tooth 170. hi these conditions, the rear arm 41b of seal- 41 finds itself directly above a trigger tooth 51, and therefore the arm 41b is being raised-up when the trigger is pulled. Otherwise, when the sear is not engaged by the hammer tooth 17c, and is brought forwards by plunger 50, the arm 4111 does not engage with the trigger tooth 51 (FIG. 1), under certain conditions, however, described later, the sear arm 41b can be engaged by a step 52 (FIGS. 3 and 4) adjacent to tooth 51.

Functioning of the above described mechanism is as follows: as usual the breech bolt is first pulled back by hand, to introduce a cartridge into the barrel. In this movement which does not differ from a recoil produced by a shot, the breech is brought back as shown in FIG. 1. The delay mass 18 and hammer 17 are swung completely back (clockwise in FIG. 1'); and the delay mass gets locked by pawl 32. Pin 26 of hammer toggle link falls below the dead centre, and thereforethe hammer tends to rotate clockwise under action of spring 28 and rod 27 and rests against a suitable limit stop (not shown).

During the successive phase, when the breech bolt moves forward, cam 36 engages unlocking lever 35, and by depressing it causes pawl 32 to free the delay mass 18,

which, under action of spring 25 and rod 23 swings coun- 'togglelin'k. Immediately the dead centre is passed, the

hammer tooth 17c engages arm 41a of scar 41; the latter recedes overcoming action o'f plunger 50 and comes to rest in condition shown in FIG. 2. The plunger 50 and its spring act therefore as a shock absorber for hammer 17. Now, the trigger mechanism being cocked, the further action depends on the setting of the selector 45. FIG. 1 shows the selector in safety position, where the trigger arm 44 bears against the cylindrical part ofthe selector, thus locking the trigger. By turning the selector clockwise by approx. 30 as shown in FIG. 2, a limited course is given to the arm 44 which penetrates into selector cut 46. It can be seen from FIG. 2, that by pulling 4 the trigger 40, tooth 51 encounters the rear arm 41b of sear 41, and makes the said sear rotate on its pivot 16, until the hammer tooth 170 is set free and spring 28 through rod 27 swings the hammer anticlockwise against the rear extremity of firing pin 21 located in the breech bolt 20, causing a shot to be fired. I

Simultaneously, sear 41 slides forward under action of the spring loaded plunger 50, thus removing the rear arm 41b from'the path of tooth 51. After a shot has been fired, the breech bolt recoils, repeating all cocking mo* tions as already described with reference to FIG. 1, the only difference being that if the shooter does not release the trigger, the situation is as shown on'FIG. 3. Consequently, when the hammer tooth -17c strikes against the forearm 41a, moving backwards the sear 41, its rear arm 41b slides on the step 52 and come to rest against tooth 51 (as shown on FIG. 3) locking the hammer 17. To fire another shot, the shooter must release the trigger, which under action of its spring 42 returns to the neutral position-allowing the sear 41 to slide backwards to conditions shown in FIG. 2. By pulling the trigger again, the abovedescribed cycle will be repeated for semi-automatic firing.

For full automatic or continuous fire the selector 45 is further rotated, to take the position shown on FIG. 4. Then, the trigger arm 44 can penetratecompletely into the cut 46, i.e. the trigger can be pulled further back than it was possible for single shot action. It can be seen from FIG. 4 that in these conditions the sear 41 is tilted by the trigger step 52, so as to remove the, front arm 41a away from the path of the hammer tooth 17c. Consequently, the hammer will not be stopped by the sear, all the time the shooter keeps pulling the trigger. The rate of fire results relatively low, as the hammer 1'7 is being released only after the delay mass 18 has completed a major part of its forward course. Also, unlocking of the delay mass to allow for its swing, occurs only [after the breech bolt returns from its recoiled position (FIG. 1),, and towards the end of its locking stroke, by means of cam 36, depresses the lever 35. Thus the maximum distance of the cam 36 from lever 35 constitutes one of parameters which determine the rate of fire.

The expression forwards, backwards" and similar, used in this description, refer as it is usually intended in firearms, where forward is the direction of shooting. It is also to be understood, that the invention shall not be limited only to the embodiment depicted on the drawmgs, exception being made for the limitations resulting from the appended claims.

What I claim is:

1 In a firing mechanism in an automatic firearm, a reciprocating breech bolt including a firing pin therein, a casing positioned below the path of the breech bolt, a first and a second pivot in the casing, a hammer swing able on the first pivot between a recoil condition and striking condition on a path intersecting the path of the breech bolt whereby the recoil stroke of the breech bolt displaces the hammer towards recoil condition of the latter, spring-loaded means jointly providing with the hammer a toggle'link causing the hammer to snap into its first and second mentioned condition through a dead pointcondition, a spring-loaded delay mass swingable on the said first pivot adjacent the hammer between a recoil condition and a firing condition on a path intersecting the path of the breech bolt whereby the recoil stroke of the breech bolt displaces the delay mass to its recoil condition, spring-loaded lock means locking the mass in its recoil condition, a cam surface on the breech bolt causing the said lock means to unlock the mass on return of the breech to its firing condition thereby to cause the spring- .loaded mass to swing into its firing condition, a lost mocondition through its dead point condition as the mass is about to reach its firing condition; a trigger swing'able on the said second pivot from a safety condition to a continuous firing condition through a single shot condition and vice-versa, a tooth projecting from the trigger, a tooth radially projecting from the hammer, a two-armed sear extending with its arms between the paths of the two teeth, the said sear having an eyelet therein elongated in the general direction of the arms accommodating the said second pivot whereby the sear is shiftable by the tooth on the hammer acting on one of its arms to intersect, with its opposite arm, the path of the tooth on the trigger while retaining the hammer in cocked condition, and spring means acting on the sear to shift the latter in the direction of the first mentioned arm and cause the first mentioned arm to intersect the path of the tooth on the hammer, the said tooth on the trigger acting on the sear to swing the latter on the said second pivot thereby to bring the first mentioned arm out of the path of the tooth on the hammer.

2. In the mechanism as claimed in claim 1, the said lost motion connection including an abutment surface on the delay mass and a finger laterally protruding from the hammer into the path of the said surface.

3. In the mechanism as claimed in claim 1, the said lock means comprising a tooth on the delay mass, a spring-loaded locking pawl normally protruding into the path of said tooth on the delay mass, and an unlocking lever swingable on the first pivot acting on the pawl to remove the latter from the path of said tooth on the delay mass, the said unlocking lever protruding into the path of the cam means on the breech bolt for actuation by the cam means on return of the breech to its firing condition; and the said lost motion connection including an abutment surface on the delay mass angularly spaced from said tooth on the delay mass, and a finger laterally protruding from the hammer into the path of the said surface at a location between the said surface and said tooth on the delay mass.

4. In the mechanism as claimed in claim 1, a step on the trigger adjacent the tooth on the latter capable of engaging the said opposite arm on the scar on displacement of the trigger to its continuous firing condition thereby bringing the said first mentioned arm on the sear out of contact with the tooth on the hammer, and a selector member limiting the pull of the trigger for a single shot action to an extent less than that necessary for the said step to bring the said first mentioned arm out of intersection with the said tooth on the hammer.

No references cited. 

